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/*
* Rivest's Package Tranform
*
* (C) 2009 Jack Lloyd
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
#include <botan/package.h>
#include <botan/filters.h>
#include <botan/ctr.h>
#include <botan/loadstor.h>
namespace Botan {
void aont_package(RandomNumberGenerator& rng,
BlockCipher* cipher,
const uint8_t input[], size_t input_len,
uint8_t output[])
{
if(input_len <= 1)
throw Encoding_Error("Package transform cannot encode small inputs");
const size_t BLOCK_SIZE = cipher->block_size();
if(!cipher->valid_keylength(BLOCK_SIZE))
throw Invalid_Argument("AONT::package: Invalid cipher");
// The all-zero string which is used both as the CTR IV and as K0
const std::string all_zeros(BLOCK_SIZE*2, '0');
SymmetricKey package_key(rng, BLOCK_SIZE);
Pipe pipe(new StreamCipher_Filter(new CTR_BE(cipher), package_key));
pipe.process_msg(input, input_len);
const size_t remaining = pipe.remaining();
BOTAN_ASSERT_EQUAL(remaining, pipe.read(output, remaining), "Expected read size");
// Set K0 (the all zero key)
cipher->set_key(SymmetricKey(all_zeros));
secure_vector<uint8_t> buf(BLOCK_SIZE);
const size_t blocks =
(input_len + BLOCK_SIZE - 1) / BLOCK_SIZE;
uint8_t* final_block = output + input_len;
clear_mem(final_block, BLOCK_SIZE);
// XOR the hash blocks into the final block
for(size_t i = 0; i != blocks; ++i)
{
const size_t left = std::min<size_t>(BLOCK_SIZE,
input_len - BLOCK_SIZE * i);
zeroise(buf);
copy_mem(buf.data(), output + (BLOCK_SIZE * i), left);
for(size_t j = 0; j != sizeof(i); ++j)
buf[BLOCK_SIZE - 1 - j] ^= get_byte(sizeof(i)-1-j, i);
cipher->encrypt(buf.data());
xor_buf(final_block, buf.data(), BLOCK_SIZE);
}
// XOR the random package key into the final block
xor_buf(final_block, package_key.begin(), BLOCK_SIZE);
}
void aont_unpackage(BlockCipher* cipher,
const uint8_t input[], size_t input_len,
uint8_t output[])
{
const size_t BLOCK_SIZE = cipher->block_size();
if(!cipher->valid_keylength(BLOCK_SIZE))
throw Invalid_Argument("AONT::unpackage: Invalid cipher");
if(input_len < BLOCK_SIZE)
throw Invalid_Argument("AONT::unpackage: Input too short");
// The all-zero string which is used both as the CTR IV and as K0
const std::string all_zeros(BLOCK_SIZE*2, '0');
cipher->set_key(SymmetricKey(all_zeros));
secure_vector<uint8_t> package_key(BLOCK_SIZE);
secure_vector<uint8_t> buf(BLOCK_SIZE);
// Copy the package key (masked with the block hashes)
copy_mem(package_key.data(),
input + (input_len - BLOCK_SIZE),
BLOCK_SIZE);
const size_t blocks = ((input_len - 1) / BLOCK_SIZE);
// XOR the blocks into the package key bits
for(size_t i = 0; i != blocks; ++i)
{
const size_t left = std::min<size_t>(BLOCK_SIZE,
input_len - BLOCK_SIZE * (i+1));
zeroise(buf);
copy_mem(buf.data(), input + (BLOCK_SIZE * i), left);
for(size_t j = 0; j != sizeof(i); ++j)
buf[BLOCK_SIZE - 1 - j] ^= get_byte(sizeof(i)-1-j, i);
cipher->encrypt(buf.data());
xor_buf(package_key.data(), buf.data(), BLOCK_SIZE);
}
Pipe pipe(new StreamCipher_Filter(new CTR_BE(cipher), package_key));
pipe.process_msg(input, input_len - BLOCK_SIZE);
const size_t remaining = pipe.remaining();
BOTAN_ASSERT_EQUAL(remaining, pipe.read(output, remaining), "Expected read size");
}
}
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